This topic, about who is stronger between Itachi, Jiraiya and Orochimaru, reminded me that just after the infamous line by Itachi "he can kill us" or whatever it was... many theorized that Itachi was a Konoha spy.

Farfetched now actually, but at the time it seemed reasonable.

My current guess is that, despite being a Sannin, Jiraiya's tactics were unknown to Itachi, but he had a good reputation. Despite having been Oro's "teammate" in Akatsuki, he could have never learnt anything about the other Sannins.

I was going to say that Jiraiya has been the only one to "seal" the Amaterasu's fires... but then I remembered that is the only time Itachi has used Amaterasu...